A 2% Zn cut-off was used for the estimate, which is consistent with other Mississippi Valley Type deposits with similar infrastructure and with the costs of mining and processing for the Olza Project. It is based on median forecast long term metal prices for Zn US$1.00-1.10/lb and for Pb of US$0.95-1.00/lb, preliminary average life-of-mine recoveries of 89% Zn and 88.5% Pb and total on-site mining + milling costs of $47.42/tonne milled.
Reasonable prospects of eventual economic extraction were assessed prior to the resource tally. For all modelled zones, assayed intersections were assessed on a hole-by-hole basis to ensure an adequate mineable thickness. Based on proposed mining method, contemplated mining equipment and preliminary recoveries, grade-thickness criteria were assessed for all estimated blocks using a threshold of 3m-%. Mineralized zones of insufficient thickness and/or grade were discarded. Blocks meeting these criteria were further assessed based on proximity both to other mineable zones and likely underground development - small, isolated groupings of blocks were discarded and did not contribute to the overall resource tally.
 

Rathdowney is advanced in its documentation and mitigation planning for environmental assessment, and its planning for mine and materials handling facilities are being done with consideration of environment conditions and local opportunities. The Company has engaged with stakeholders throughout its project work. It is not expected that there will be extensive legal, political, environmental or other issues that could materially affect the potential development.
 

A total of 1,061 drill holes were used for the estimate of which 793 holes are historical and 268 were drilled by Rathdowney. The estimate was completed using Vulcan™ v2023.1 software to interpolate values for zinc, lead, and bulk density into the block model using an inverse distance squared (ID2) function. Interpolation was carried out in a single pass using search strategies and ranges which have been developed geostatistically. Block grades were interpolated using a minimum of three samples from a minimum of two drill holes, and sample selection was governed by zone morphology to ensure appropriate correlation. A classification of inferred was assigned to the entire resource based on the geostatistical analysis of the Olza Zn-Pb data, drill hole spacing and spatial uncertainty associated with the locations of the historical drill collars.
 

The increase in the estimate of mineral resources from the previous estimate in 2014 is not considered to be material.
 

The resource was estimated under Canadian regulation NI 43-101, by David Gaunt, P.Geo., a qualified person who is not independent of the Company. The effective date of the estimate is July 2023. Mr Gaunt has reviewed this disclosure.